Estimation of leak rates through a through-wall cracked pipes using Moody's critical flow model

To introduce Leak-Before-Break (LBB) concept into the piping design standard of the LWR pressure boundary piping, LBB research and verification test programs are actively conducted in many nuclear electricity generating countries. It is an important subject to evaluate the leak rate through a through-wall cracked pipes for the verification of LBB. At JAERI, a leak test program has started in 1987 in order to measure leak rates of coolant through cracks in 4- and 6-inch diameter pipes and through slit specimens. Using the Moody's critical flow model, a computer program to evaluate a leak rate through a through-wall cracked pipes has been developed in order to determine the crack angle of test pipes in the leak test. This report describes the Moody's critical flow model, the outline of the computer program and the results of preliminary calculations. (author)